The present invention relates to the development of a hand-held, pneumatically actuated mallet. Prior art workers have heretofore devised various types of electro-pneumatic hammers. Such hand-held electro-pneumatic hammers are taught, for example, in U.S. Pat. Nos. 3,921,729; 3,926,266 and 4,064,949. These tools, however, are completely different in concept and operation from the pneumatic mallet of the present invention. The typical electro-pneumatic hammer provides an air cushion within the bore of a cylinder between a driving piston and a striking piston. The driving piston is operated by an electric motor and a crank. The striking piston operates on an appropriate tool removably mounted in the forward end of the electro-pneumatic hammer.
Prior art workers have also devised numerous types of pneumatic fastener driving tools. Such tools are used to drive headed or headless nails, staples and other appropriate types of fasteners.
As is well known in the art, pneumatic fastener driving tools basically comprise a housing having a handle portion. The housing contains a main cylinder having a piston/driver assembly. The housing also contains control valve means for actuating the piston/driver assembly in the main cylinder. The control valve means, in turn, is operated by a manual trigger generally located near the juncture of the housing and its handle portion. The pneumatic fastener driving tool additionally has a guide body mounted on the housing beneath the main cylinder. The guide body provides a drive track for the driver and the fasteners to be driven. The fasteners are located in a magazine communicating with the guide body and its drive track. In the most usual structure, the housing handle portion is hollow and provides a reservoir for air under pressure together with means to connect the reservoir to a source of air under pressure.
The more modern examples of such pneumatic fastener driving tools are equipped with a mode selector valve which enables the fastener driving tool to operate in a "single-fire" or an "auto-fire" mode of operation. In the single-fire mode of operation, a fastener is driven upon each actuation of the manual trigger. In an auto-fire mode of operation, fasteners are driven continuously, so long as the trigger is held in its actuated position.
An exemplary, but non-limiting, embodiment of such a pneumatic fastener driving tool is set forth in U.S. Pat. No. 3,278,104. For purposes of description, the teachings of this patent are herein incorporated by reference. In pneumatic fastener driving tools of the type just described, the housing and its handle portion, the main cylinder, the piston/driver assembly, the control valve means, the manual trigger, the means for connection to a source of air under pressure and the firing mode selector valve (if present) may be considered a pneumatic motor. It is this type of pneumatic motor which is utilized in the mallet of the present invention.
The present invention is based upon the discovery that a hand-held tool in the form of a pneumatically actuated mallet can be provided, utilizing such a pneumatic motor provided with a modified guide body and mallet assembly. The mallet tool of the present invention can be manufactured as such, or an existing pneumatic fastener driving tool can be converted to a pneumatic mallet, as will be described hereinafter. The mallet of the present invention is simple in construction and operation, and limits human fatigue by eliminating the necessity for repeated swinging of the operator's arm. The mallet also resolves ergonomic problems related to Carpal Tunnel Syndrome, an occupational disorder frequently resulting from constant swinging of the arm and wrist and constituting inflammation, chronic pain and sometimes permanent injury to the synovial sheath protecting the tendons of the wrist and the median nerve passing through the wrist.